The present invention is directed to devices and methods for generating light with electrodeless high intensity discharge (HID) lamps. More particularly, the present invention provides high intensity discharge lamps driven by a radio-frequency source without the use of electrodes inside a gas-filled vessel (bulb) and related methods. Merely by way of example, such electrodeless HID lamps can be applied to applications such as parking lots, street lights, warehouses, stadiums, security, ports and harbors, large and small buildings, vehicle headlamps, billboard lighting, building facade lighting, airports, bridges, agriculture and horticulture lighting, architectural lighting, stage and entertainment lighting, medical illumination, microscopes, projectors and displays, ultraviolet (UV) water treatment, UV curing, any combination of these, and the like.
High intensity discharge lamps provide extremely bright and broad spectrum light source. The typical conventional electroded HID manufactured today contains a bulb with a mixture of gas and metal halides that are excited to form a plasma using a high current passed through closely-spaced electrodes. This arrangement, however, suffers from deterioration of the electrodes over time, and therefore a bulb with limited lifetime.
Electrodeless HID lamps driven by radio frequency (RF) sources have been proposed in the prior art. In all embodiments, the RF source is separated from a lamp module or housing in which the bulb is mounted and configured. This lamp housing is usually designed and configured to maximize the amount of RF energy incident on the bulb. This energy excites (i.e. heats) the gas and materials in the bulb to create an intense plasma that converts the RF energy into infrared, visible, and UV light. In all cases, however, a portion of the provided RF energy cannot reach the bulb or is not absorbed by the plasma and instead is released as propagating wave radiation or remains localized as non-propagating RF electromagnetic fields in the vicinity of lamp housing.
This unused energy can be troublesome. Localized fields can create problems when the lamp engine is placed in a fixture as the structural components, such as reflectors and metal covers, can interact with the fields and create feedback with the RF source. Such feedback can interfere with sensors and components in the RF source causing lamp malfunction and failure. Radiated energy manifests as electromagnetic interference (EMI) in nearby electronic and wireless devices. These EMI emissions can be disruptive and often are regulated by governmental bodies such as the Federal Communications Commission (FCC).
Clearly, management of such unused energy is an important aspect of lamp operation. In the following invention, we introduce field suppression probes that capture and suppress this unused energy, preventing both feedback issues and radiating emissions. Moreover, the probes also improve confinement of the energy to help increase transfer of energy to the plasma.